STAC9708 datasheet(35/56 Pages) ETC

35 / 56 page

SigmaTel, Inc.

Preliminary

STAC9708/11

10/02/98

Figure 12. Example of STAC9708/11 Powerdown/Powerup flow

PR0=1

PR1=1

PR2=1

PR4=1

Default

Normal

ADCs off

PR0

DACs off

PR1

Analog off

PR2 or PR3

Digital I/F off

PR4

Shut off

Coda-link

PR0=0

ADC=1

PR1=0

DAC=1

PR2=0

ANL=1

Warm Reset

Cold Reset

Ready =1

The above figure illustrates one example procedure to do a complete powerdown of STAC9708/11. From normal

operation, sequential writes to the Powerdown Register are performed to power down STAC9708/11 a piece at a

time. After everything has been shut off, a final write (of PR4) can be executed to shut down the AC-Link. The

part will remain in sleep mode with all its registers holding their static values. To wake up, the AC'97 controller

will send an extended pulse on the sync line, issuing a warm reset. This will restart the AC-Link (resetting PR4

to zero). The STAC9708/11 can also be woken up with a cold reset. A cold reset will reset all of the registers to

their default states. When a section is powered back on, the Powerdown Control/Status register (index 26h)

should be read to verify that the section is ready (stable) before attempting any operation that requires it.

Figure 13. STAC9708/11 Powerdown/Powerup flow with analog still alive

PR0=1

PR1=1

PR4=1

Normal

ADCs off

PR0

DACs off

PR1

Digital I/F

off PR4

Shut off

Coda-link

PR0=0

ADC=1

PR1=0

DAC=1

Warm Reset

The above figure illustrates a state when all the mixers should work with the static volume settings that are

contained in their associated registers. This configuration can be used when playing a CD (or external LINE_IN

source) through STAC9708/11 to the speakers, while most of the system in low power mode. The procedure for

this follows the previous except that the analog mixer is never shut down.

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